How to fix into internal wall insulation? – Can I Just Ask? | Ep.32

Fixing into internal wall insulation is something that’s best thought about before the installation goes in, not after. The ideal approach wherever possible is to reroute services and fixings away from external walls altogether — the less metal penetrating through insulation, the better for thermal performance, and chasing services into a finished insulated wall is destructive and labour-intensive. Where fixings into the insulated wall can’t be avoided, the right solution depends entirely on the weight involved, and there are three clear tiers.

For the lightest loads — a picture or something weighing a kilo or two — a short wood screw straight through the plasterboard or clay plaster finish is perfectly adequate. For mid-range loads up to around five kilograms, spiral anchor fixings are the preferred option: a nylon corkscrew plug that screws into the insulation layer only, dispersing the load within the wood fibre rather than pulling back to the masonry. Installation requires drilling a pilot hole and cutting a small slot at the surface so the spiral fins can pass through the finish without breaking off — but once in, they hold reliably and are well suited to curtain poles, small speakers, and artwork. For heavy items — kitchen units, radiators, anything upwards of 20kg per fixing point — Fischer Thermax fixings are the answer: a thermally broken head with a masonry plug and screw that passes all the way through the insulation and anchors back into the wall behind, finishing flush with the plaster surface so items can be screwed directly into the head.

The picture changes significantly with a batten-based system like the NatureWall. Embedding timber battens within a direct-plastered insulation system introduces repeating thermal bridges and places timber in conditions it doesn’t handle as well as wood fibre — neither of which is desirable. But a system designed from the outset with a batten framework separated from the insulation layer sidesteps both problems, allowing items to be fixed directly to the battens in exactly the same way as any conventional wall, with no specialist fixings required and no compromise to the insulation layer whatsoever.